Preparation and properties of cellulose/silver nanoparticle composites with in situ-generated silver nanoparticles using Ocimum sanctum leaf extract

In the present work, silver nanoparticles were in situ-generated in cellulose matrix using Ocimum sanctum leaf extract as a reducing agent. Regenerated wet cellulose films were first immersed in O. sanctum leaf extract and then it was allowed to diffuse into the films. The leaf extract–diffused wet films were dipped in different concentrated aq.AgNO₃ solutions. The leaf extract inside the wet films reduced AgNO₃ into nanosilver. The dry composite films were black in color. Some of the nanoparticles were also formed outside the film in the solution. The nanoparticles were viewed by transmission electron microscopy and scanning electronic microscopy techniques. The composite films showed good antibacterial activity. The cellulose, matrix, and the composite films were characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis techniques. The tensile properties of the composite films were higher than those of the matrix. These biodegradable films can be used for packaging and medical purposes.     

Effect of sunlight on the preparation and properties of cellulose/silver nanoparticle composite films by in situ method using Ocimum sanctum leaf extract as a reducing agent

Cellulose/silver nanoparticle composite films with in situ-generated silver nanoparticles (AgNPs) were prepared using Ocimum sanctum leaf extract as a reducing agent in the absence and presence of sunlight and were characterized by SEM, FTIR, XRD, and antibacterial tests. Sunlight hastened up the preparation of these composite films. The average size of the in situ-generated AgNPs was reduced by the sunlight. The antibacterial activity and other properties of the composites were enhanced by the sunlight. The cellulose/AgNP composite films with improved properties by sunlight can be considered for medical purpose as antibacterial dressing materials.     

Preparation and Properties of Cellulose/Waste Leather Buff Biocomposites

The aim of the present work was to utilize waste leather buff (WLB) as filler in cellulose and make biocomposites for packaging applications such as wrappers. Cellulose was dissolved in the environmentally friendly ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). To this solution, WLB was added in amounts of 5 to 25 wt.% of cellulose. The cellulose and cellulose/WLB composite films were prepared by regenerating the corresponding cast solutions in a water coagulation bath followed by washing and drying. These films were tested for their tensile properties, thermal stability, and morphology. The tensile modulus and strength of the composite films were lower than those of the matrix. The lowering of the tensile modulus and strength with increasing WLB loading was attributed to the random orientation of the leather fibers of WLB in the composites. However, the % elongation at break of the composite films was found to be higher than that of the matrix and increased with increasing WLB content. The possible interaction between the matrix and WLB filler was probed using FT-IR analysis. The thermal stability of the composite films was higher than that of the matrix. The increase in thermal stability of the composite films was attributed to cross-linked collagen protein leather fibers in WLB. The fractographs of the composite films indicated good interfacial bonding between cellulose and leather fibers of WLB. These composite films may be considered for packaging and wrapping applications.     

In situ generation of silver nanoparticles in cellulose matrix using Azadirachta indica leaf extract as a reducing agent

In the present work, silver nanoparticles (AgNPs) were in situ generated in cellulose matrix using leaf extract of Azadirachta indica as a reducing agent. The cellulose/AgNP composite films prepared were characterized by FTIR, X-ray diffraction (XRD), scanning electron microscope, and antibacterial tests. The infrared spectra indicated the association of organic materials with silver nanoparticles to serve as capping agents. Scanning electron micrographs showed that synthesized silver nanoparticles were nearly uniform and spherical in shape with diameter in the range of 61–110?nm. XRD confirmed the formation of AgNPs and Ag–O nanoparticles. The nanocomposite films showed good antibacterial activity against Escherichia coli bacteria.     

Tensile,thermal, and antibacterial characterization of composites of cellulose/modified Pennisetum purpureum natural fibers with in situ generated copper nanoparticles

Eco-friendly all cellulose composites were developed using cellulose as matrix and nanocomposite (in situ generated copper nanoparticles modified Napier Grass Fibers (NGFs)) as fillers for the antibacterial applications. The content of the nanocomposite filler was increased from 1?wt.% to 5?wt.% in the cellulose matrix. All these composites were characterized by Scanning Electron Microscopy (SEM), Tensile, Thermo Gravimetric Analysis (TGA), and antibacterial tests. SEM-EDX analysis revealed the in situ generation of copper nanoparticles on the surface of the films. Further, all cellulose composites showed good thermal stability. A minimum of 30% increase in char residue was observed in all cellulose nanocomposites compared to matrix. Antibacterial analysis indicated an excellent clear zone formation against both Gram Negative (Escherichia coli) and Gram Positive (Staphylococcus) bacteria. Hence, all these cellulose nanocomposite films can be considered as antibacterial packaging and dressing materials in medical field.     

Structure and properties of regenerated cellulose/tourmaline nanocrystal composite films

Nanocomposite films were successfully prepared from cellulose and tourmaline nanocrystals with mean diameters of 70 nm in a 1.5 M NaOH/0.65 M thiourea aqueous solution by coagulation with 5 wt % CaCl₂ and then a 3 wt % HCl aqueous solution for 2 min. The structure and properties of the composite films were characterized by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, dynamic mechanical analysis (DMA), differential scanning calorimetry (DSC), and tensile testing. The results indicated that the tourmaline nanocrystals were dispersed in a cellulose matrix, maintaining the original structure of the nanocrystals in the composite films. The loss peaks (tan δ) in the DMA spectra and the decomposition temperatures in the DSC curves of the composite films were significantly shifted toward low temperatures, suggesting that the nanocrystals broke the partial intermolecular hydrogen bonds of cellulose, and this led to a reduction in the thermal stability. However, the nanocomposite films exhibited a homogeneous structure and dispersion of the nanocrystals. When the tourmaline content was in the range of 4–8 wt %, the composite films possessed good tensile strength (92–107 MPa) and exhibited obvious antibacterial action against Staphylococcus aureus. This work provides a potential way of preparing functional composite films or fibers from cellulose and nanoinorganic particles with NaOH/thiourea aqueous solutions. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 367–373, 2004     

Structure and properties of the nanocomposite films of chitosan reinforced with cellulose whiskers

Bio‐based nanocomposite films were successfully developed using cellulose whiskers as the reinforcing phase and chitosan as the matrix. Cellulose whiskers, with the lengths of 400 ± 92 nm and diameters of 24 ± 7.5 nm on average, were prepared by hydrolyzing cotton linter with sulfuric acid solution. The effects of whisker content on the structure, morphology and properties of the nanocomposite films were characterized by SEM, XRD, FTIR, UV‐vis spectroscopy, DMA, TG, tensile testing, and swelling experiment. The results indicated that the nanocomposites exhibited good miscibility, and strong interactions occurred between the whiskers and the matrix. With increasing whisker content from 0 to 15–20 wt %, the tensile strength of the composite films in dry and wet states increased from 85 to 120 MPa and 9.9 to 17.3 MPa, respectively. Furthermore, the nanocomposite films displayed excellent thermal stability and water resistance with the incorporation of cellulose whiskers. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 1069–1077, 2009     

High strength cellulose composite films reinforced with clay for applications as antibacterial materials

High strength cellulose composite films with antibacterial activities were prepared by dispersing montmorillonites (MMT) into cellulose solution in LiOH/urea aqueous solvent followed by regeneration in ethanol coagulation bath, and then by soaking in 5 wt% hexadecylpyridine bromide ethanol solutions to induce the antibacterial action. The cellulose/MMT composite films were characterized by field emission scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, FTIR, UV-spectra, wide angle X-ray diffraction and mechanical test. The results revealed that MMT was dispersed well in the cellulose matrix to form layer structure with a thickness of approximately 3 nm. The mechanical properties of the cellulose/MMT composite films were significantly improved to achieve 132 MP for tensile strength as a result of the MMT delamination. The hexadecylpyridine bromide was fixed well in the cellulose/MMT matrix through cation exchange, leading to the excellent antibacterial activities against Staphylococcus aureus and Escherichia coli, which is important in their practical applications.     

Preparation and characterization of tamarind nut powder with in situ generated copper nanoparticles using one-step hydrothermal method

Tamarind nut powder (TNP) from kitchen waste of tamarind nuts was modified with in situ generated copper nanoparticles (CuNPs) using hydrothermal method. The modified TNP had spherical CuNPs with an average size of 84?nm. The thermal stability of the modified TNP was lower than that of the TNP due to the catalytic activity of the in situ generated CuNPs in lowering the thermal stability. Further, it exhibited significant antibacterial activity against both the Gram negative and Gram positive bacteria and hence can be used as low-cost filler to prepare antibacterial hybrid polymer nanocomposites for packaging and medical applications.     

Preparation and Characterization of Nanocomposites of Carboxymethyl Cellulose Reinforced with Cellulose Nanocrystals

Summary: Cellulose nanocrystals (CNC) were extracted from Kraft pulp of Eucalyptus urograndis. The CNC were isolated by acid hydrolysis with H₂SO₄ 64% (w/w) solution, for 20 minutes at 45 °C. The morphology and crystallinity of the CNC were investigated by atomic force microscopy (AFM) and X-ray diffraction (XRD), respectively. The AFM image supports the evidence for the development of crystals of cellulose in nanometric scale. These nanoparticles were used as reinforcement material in carboxymethyl cellulose (CMC) matrix. Nanocomposites films were prepared by casting. The nanocomposites were characterized by thermal (TGA) and mechanical (DMA) analyses. A large reinforcing effect of the filler was observed. The tensile strength of nanocomposites was significantly improved by 107%, the elongation at break decreased by 48% and the thermal resistance increased slightly. The improvements in thermo-mechanical properties suggest a close association between filler and matrix.     

纤维素/全硫化弹性纳米粒子复合膜的制备与性能

利用碱脲溶剂低温溶解纤维素,在该体系中掺杂一定比例的全硫化羧基丁苯弹性纳米粒子,制备了纤维素/全硫化弹性纳米粒子复合膜.通过透射电镜、扫描电镜、WAXD、固体核磁共振、热分析和力学性能测试等对该复合膜的结构和性能进行了表征.结果表明,全硫化羧基丁苯弹性纳米粒子(CSB ENP)均匀的分散在具有微纳孔洞结构的纤维素基体中.CSB ENP的引入对纤维素再生过程中的结晶性影响不大.纤维素/全硫化弹性纳米粒子复合膜具有良好的透光性,并且热稳定性也有所提高.加入少量的CSB ENP可以增韧纤维素膜,且能保持良好的力学性能.当CSB ENP的含量为5 wt%时复合膜的断裂拉伸强度和断裂伸长率同时得到了提高.     

Nanocomposite films based on cellulose reinforced with nano-SiO2: microstructure, hydrophilicity, thermal stability, and mechanical properties

Microcrystalline cellulose/nano-SiO₂ composite films have been successfully prepared from solutions in ionic liquid 1-allyl-3-methylimidazolium chloride by a facile and economic method. The microstructure and properties were investigated by Fourier transform infrared spectroscopy, wide-angle X-ray diffraction, scanning electron microscopy, transmission electron microscopy, water contact angle, thermal gravimetric analyses, and tensile testing. The results revealed that the well-dispersed nanoparticles exhibit strong interfacial interactions with cellulose matrix. The thermal stability and tensile strength of the cellulose nanocomposite films were significantly improved over those of pure regenerated cellulose film. Furthermore, the cellulose nanocomposite films exhibited better hydrophobicity and a lower degree of swelling than pure cellulose. This method is believed to have potential application in the field of fabricating cellulose-based nanocomposite film with high performance, thus enlarging the scope of commercial application of cellulose-based materials.     

SERS detection of ceftriaxone and sulfadimethoxine using copper nanoparticles temporally protected by porous calcium carbonate

The authors describe a new composite based on SERS-active copper nanoparticles (CuNPs; 10?±?2 nm) incorporated into calcium carbonate microspheres (CaCO₃-CuNPs; 3.4?±?0.3 μm). The CaCO₃ coating acts as a temporal protector of CuNPs against oxidation. Incorporated CuNPs have significantly improved stability during storage and a month-long shelf lifetime. The composite was used for SERS detection of rhodamine 6G and two antibacterial drugs (ceftriaxone and sulfadimethoxine). Two analytical formats, one with and one without solid phase extraction, are introduced to demonstrate the flexibility of the method. Both formats imply the dissolution of CaCO₃ matrix before SERS analysis to release CuNP used as SERS substrate. The study of the influence of pH value and acid nature on the SERS signal demonstrated that HCl is the most efficient candidate to release the CuNPs. Sensitivity (expressed as LOD) is shown to be improved by more than one order when solid phase extraction is used. The average SERS enhancement factor is 10^7 which makes the material efficiency comparable to the one of silver nanoparticles. The LOD (<5 μM), precision (RSDs between 20 and 24% at LOD levels), and trueness (apparent recoveries 84–113%) for the two antibiotics (ceftriaxone and sulfadimethoxine) make the method quite useful for quantitative analysis and therapeutic drug monitoring at physiologically relevant concentrations.

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Graphical abstract A composite with temporally stable copper nanoparticles was synthesized, studied, and used for SERS detection of two antibacterial drugs. The analytical efficiency of the composite was found appropriate for quantitative analysis due to Raman enhancement comparable with silver nanostructures.

     

Effect of copper nanoparticles on the properties of SEBS/PP compounds

This study evaluated the adoption of copper nanoparticles (CuNPs) as an antimicrobial agent in thermoplastic elastomer compounds (TPEs) based on styrene-(ethylene-butylene)-styrene triblock copolymer (SEBS) and polypropylene (PP) for use in the fabrication of automotive air-conditioning systems. The nanocompounds were prepared using a co-rotating double screw extruder and CuNPs were pre-dispersed in polypropylene at weight proportions of 0%, 0.6% and 1.0%. The physical (density), mechanical (tensile and hardness), thermal (differential scanning calorimetry and thermogravimetry) and antimicrobial properties were evaluated on injection molded plates. The antimicrobial properties were evaluated for the bacteria Staphylococcus aureus and Escherichia coli and fungal species commonly found in automotive air conditioners. The results from antibacterial tests showed a reduction of 99.9% in counts of both bacteria tested. There was no fungal growth on the loaded TPE surface. At the tested levels, the addition of CuNPs did not cause significant variations in the TPE properties evaluated.     

Sugar beet cellulose nanofibril-reinforced composites

Cellulose was isolated from sugar beet chips, a by-product of sugar production, by wet chemistry. Further processing of the cellulose with a high-pressure homogeniser led to the disruption of cell walls into nanofibrils. Cellulose sheets obtained by casting and slow evaporation of water showed higher strength and stiffness when homogenised cellulose was used compared to unhomogenised cellulose. These cellulose sheets showed significantly better mechanical performance than Kraft paper tested for reference. The addition of cellulose nanofibrils to a polyvinyl alcohol and a phenol-formaldehyde matrix, respectively, demonstrated excellent reinforcement properties. The best mechanical performance was achieved for a composite with a phenol-formaldehyde resin content of 10%, which showed a tensile strength of 127 MPa, a modulus of elasticity of 9.5 GPa, and an elongation at break of 2.9%.     

Biogenesis of copper nanoparticles using peel extract of Punica granatum and their antimicrobial activity against opportunistic pathogens

Copper nanoparticles (CuNPs) were biologically synthesized using peel extract of Punica granatum as reducing agent as well as capping agent. On treatment of aqueous solutions of CuSO₄·5H₂O with peel extract of P. granatum, stable CuNPs were formed. UV-Visible spectrophotometer analysis confirmed the formation of CuNPs. The synthesized nanoparticles were characterized with Fourier transform infrared spectroscopy, particles size analyzer and transmission electron microscopy (TEM). The electron microscopy analysis of CuNPs indicated that they ranged in size from 15 to 20?nm. The biologically synthesized CuNPs demonstrated high antibacterial activity against opportunistic pathogens, that is, Micrococcus luteus MTCC 1809, Pseudomonas aeruginosa MTCC 424, Salmonella enterica MTCC 1253 and Enterobactor aerogenes MTCC 2823 in vitro. Nanoparticles synthesized biologically using plant extracts have the potential to serve as possible ecofriendly alternatives to chemical and physical methods for biomedical applications and research.!     

Efficient alternative of antimicrobial nanocomposites based on cellulose acetate/Cu-NPs

The current research presents an efficient, cheap, and safe antimicrobial material for widespread use based on copper nanoparticles (Cu-NPs) loaded on cellulose acetate (CA) matrix. A reduction process of CuSO₄·5H₂O has been performed to prepare Cu-NPs. The nanosized copper particles included oxidized Cu (15–20 nm). Two different loads of Cu-NPs were used in this study, 2% and 6% mol.%. The presence of Cu-NPs incorporated with CA films slightly affected the tensile index of the films, where low and high-loaded Cu-NPs enhanced the tensile index by small values ranged from 0.640 to 0.650 and 0.667, respectively. A study on the antibacterial activity of these nanocomposites was carried out for Staphylococcus aureus, Pseudomonas aeruginosa, and Candida albicans. It has been found that CA containing Cu-NPs (2%) exhibited the highest antimicrobial activity against all test microbes including S. aeureus (21 mm), P. aeruginosa (18 mm), C. albicans (19 mm), and Aspergillus niger (15 mm). Results also revealed that CA film with 6% exhibited lower activity than film with 2% Cu-NPs. The morphological properties of CA/Cu-NPs films were characterized by scanning electron microscopy and transmission electron microscope in addition to X-ray diffraction. Low-loaded Cu-NPs showed homogenous distribution through CA matrix while, the high-loaded Cu-NPs were agglomerated through CA matrix. Thermal properties illustrated the enhancement of thermal stability of the film with increasing the loaded Cu-NPs.     

Fabrication of flexible AgNW/cellulose hybrid film with heat preservation and antibacterial properties for agriculture application

In the view of sustainable development and environmental protection, degradable agricultural films with on-demand thermal insulation properties have attracted growing research interest in the last few decades due to the deteriorating environment and extreme climate on the growth and existence of crops. Here, a general strategy has been developed to fabricate degradable silver nanowires modified cellulose (AgNW/cellulose) hybrid film with controllable thermal insulation and antibacterial properties by using plant cellulose and AgNWs as building blocks, PVA and PEG as film forming solvent, as well as their agriculture application. The results show that the AgNWs are evenly dispersed in the three-dimensional grid of cellulose, that they form a film that can withstand a certain tensile force and have good thermal stability. Due to the excellent electrical conductivity, the AgNW/cellulose hybrid films can provide excellent Joule heating, generating rapid thermal response and uniform electrical heating at a low supply voltage of 3 V. In the antibacterial tests against Escherichia coli and Staphylococcus aureus, the AgNW/cellulose hybrid films exhibited large diameters of inhibition zones, revealing the high antibacterial activity. Additionally, the AgNW/cellulose hybrid films showed highly stretchable behavior by delivering a breaking strain of 1.5% with a tensile stress of 0.45 MPa owing to the cross-linked structures of cellulose and AgNWs. Based on the above properties, this study not only provides a potential strategy for the fabrication of flexible and biodegradable agricultural films but also may provide new insights for agricultural thermal management.

     

铜(Ⅱ)络合纤维的配位结构与抗菌性

用蚕丝、粘胶纤维素、聚乙烯醇纤维在铜氨溶液中的多相配位取代反应制备了铜（Ⅱ）络合纤维．用电子自旋共振（ＥＳＲ）波谱等研究了铜（Ⅱ）络合纤维的配位结构．对金黄色葡萄球菌的抗菌实验表明：铜（Ⅱ）络合纤维的配位结构越不稳定抗菌性越强，但耐洗性将会下降．在此基础上设计了配位结构稳定性适中的柠檬酸修饰纤维素铜（Ⅱ）络合纤维     

Biocomposites based on Alfa fibers and starch‐based biopolymer

Biocomposite materials based on Alfa cellulose fibers (esparto grass plant) as reinforcing element and starch‐based biopolymer matrix were prepared and characterized in terms of mechanical performance, thermal properties, and water absorbance behavior. The fibers and the matrix were first mixed in the melted state under mechanical shearing using a plastograph and the obtained composites were molded by injection process. The tensile mechanical analysis showed a linear increase of the composite flexural and tensile modulus upon increasing the fiber content, together with a sharp decrease of the elongation at break. The fibers′ incorporation into the biopolymer matrix brings about an enhancement in the mechanical strength and the impact strength of the composite. Dynamic mechanical thermal analysis (DMTA) investigation showed two relaxations occurring at about ?30 and 35°C. The addition of Alfa fibers enhanced the storage modulus E′ before and after T_α, which is consistent with the reinforcing effect of Alfa cellulose fibers. Copyright © 2008 John Wiley & Sons, Ltd.